1. The Field of the Invention
Exemplary embodiments of the present invention relate to the field of laser optics, and, more specifically, to designs of Lens-on-Chip (LOC) and Lens-on-Post-on-Chip (LOPOC) Vertical Cavity Surface Emitting Lasers.
2. The Relevant Technology
Lasers have a wide range of applications in today's technological world. For example, lasers are used in data communications applications, in entertainment devices, as sensors, as measuring devices, and in a host of other applications. One type of laser used in these devices is the vertical cavity surface emitting laser (VCSEL). Over the years, the various devices that use VCSELs have become smaller and smaller. This has resulted in a technical challenge to engineers, who must design these components to be smaller and smaller, yet still perform to the same or better technical specifications.
One method used to miniaturize laser transmitters and laser transmission assemblies is to reduce the number of components. Another method is to make the various components themselves, smaller. For example, the beam of light that exits from a laser transmitter often needs to be focused or collimated. External lenses have been used for this purpose for many years. Recently, lens on chip (LOC) and lens on post on chip (LOPOC) technologies have been developed. LOC technology incorporates a polymer lens onto the laser chip during the wafer fabrication process. The fabrication process includes lithographically forming a region on the wafer to accept a polymer and subsequently placing the lens on the wafer using an inkjet or needle. LOPOC includes an additional polymer standoff to allow the lens to be raised from the surface of the laser chip, thus making it possible to achieve greater optical power. Previously, LOC and LOPOC were used to couple laser light from a VCSEL directly into a fiber, such as a fiber optic cable in a data communications network. This coupling was achieved on a single axis, the axis of the fiber optic cable and the axis of the light beam exiting from the VCSEL being co-linear.
One example of a basic LOPOC apparatus is shown in FIG. 1A and designated generally as reference numeral 100. Apparatus 100 includes a semiconductor emitter/detector 102. Semiconductor emitter/detector 102 can be, for example, a VCSEL, a laser beam detector, or both. Apparatus 100 further includes a polymer standoff or post 104 that maintains a lens 106 at a desired offset distance from the surface of semiconductor emitter detector 102. This allows a laser beam 108 to be focused on a desired point above apparatus 100. Alternately, or in addition to focusing the beam to a desired point, laser beam 108 can be focused on the detector via a portion of beam 108 that is reflected from lens 106.
Currently LOPOC devices only allow the beam to be directed in a straight line upward or downward, along the optical axis of the standoff and/or lens, i.e. on a single axis. However, to make the overall package smaller, it is sometimes desirable to tilt the beam or direct the beam to a point that is “off” this optical axis. FIG. 1B illustrates one prior art system used to tilt the laser beam, designated generally as reference numeral 150. System 150 includes a semiconductor emitter 152, such as a VCSEL, and a laser detector 154. An external lens 156 is used to focus a beam 158 towards a point 160 that is positioned off the optical axis of beam 158, i.e. on a different axis. A portion 162 of beam 158 is reflected back from the surface of lens 156 to detector 154.
Unfortunately, the above design to tilt the beam suffers from some significant drawbacks. Most importantly, because of the large offset between lens 156 and emitter 152, system 150 takes up an undesirable amount of space. This limits the size of the various devices that can use these VCSEL assemblies.